Abstract An assessment of the performance of the Geostationary Operational Environmental Satellite (GOES) sounder cloud-top pressure product is presented. GOES sounder cloud-top-height data were compared with values derived from a consensus cloud boundary dataset that utilizes data from a cloud lidar and a cloud radar located at the U.S. Department of Energy’s (DOE’s) Atmospheric Radiation Measurement (ARM) Program’s Cloud and Radiation Test Bed (CART) site in Lamont, Oklahoma. Comparisons were performed from April 2000 to March 2002. A temporal filtering process was applied to the cloud lidar and cloud radar output so that a representative picture of the cloud field on the same spatial scale of the GOES sounder could be derived. Comparisons between the GOES sounder and ground-based cloud boundary measurements yielded a mean difference of 1772 m and a standard deviation of 1733 m. The difference between GOES cloud-top-height and ground-based retrievals is within ±500 m for 22% of the retrievals and within...
{"title":"A Comparison of GOES Sounder– and Cloud Lidar- and Radar-Retrieved Cloud-Top Heights","authors":"James A. Hawkinson, W. Feltz, S. Ackerman","doi":"10.1175/JAM2269.1","DOIUrl":"https://doi.org/10.1175/JAM2269.1","url":null,"abstract":"Abstract An assessment of the performance of the Geostationary Operational Environmental Satellite (GOES) sounder cloud-top pressure product is presented. GOES sounder cloud-top-height data were compared with values derived from a consensus cloud boundary dataset that utilizes data from a cloud lidar and a cloud radar located at the U.S. Department of Energy’s (DOE’s) Atmospheric Radiation Measurement (ARM) Program’s Cloud and Radiation Test Bed (CART) site in Lamont, Oklahoma. Comparisons were performed from April 2000 to March 2002. A temporal filtering process was applied to the cloud lidar and cloud radar output so that a representative picture of the cloud field on the same spatial scale of the GOES sounder could be derived. Comparisons between the GOES sounder and ground-based cloud boundary measurements yielded a mean difference of 1772 m and a standard deviation of 1733 m. The difference between GOES cloud-top-height and ground-based retrievals is within ±500 m for 22% of the retrievals and within...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"5 1","pages":"1234-1242"},"PeriodicalIF":0.0,"publicationDate":"2005-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75748018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper by Riishojgaard et al. (2004) investigates the assimilation and impact of prospective Doppler wind lidar (DWL) line-of-sight (LOS) single-perspective winds in meteorological analysis. It is argued that single-component wind observations are far less effective in reducing wind analysis error than vector wind information. This work has relevance because the prospects are good that space-based DWL instruments will provide accurate wind profiles of single-perspective LOS wind profile measurements in the future. Riishojgaard et al. rightly argue that the usefulness of such winds needs to be well addressed in the design phase of space missions. The forthcoming European Space Agency Atmospheric Dynamics Mission (ADM), called Aeolus, is referred to in this context. The Riishojgaard et al. study is carried out in an idealized and very simplified framework. Our concerns are 1) that the simple framework poorly represents the characteristics of a state-of-the-art global data assimilation system for numerical weather prediction (NWP) and 2) that the DWL scenarios that are discussed have abundant and unrealistic coverage and quality. As such, their conclusions may be misleading for, and contribute little toward, the critical design considerations for an affordable space-based DWL. The results (and the quality of the analyzed wind fields) could be far more realistic and, in our view, far more favorable for LOS winds in a more carefully designed experiment. The NWP analysis problem would be severely underdetermined if it were based on the observations alone. To overcome this problem, data assimilation typically combines the information provided by the relatively sparse observations with a short-range forecast on a dense grid (Daley 1991). Because the NWP model state is poorly observed, it is critical that local observation increments are carefully distributed spatially in a wider area. This process is done based on statistical knowledge of the background error structures. In a fourdimensional variational data assimilation (4DVAR) analysis system, information on the temporal evolution of the model state is also exploited. Around any local observation, information on the multivariate spatial correlation of the background errors, as represented in the background-error covariance matrix B, is used to provide a spatially coherent update of the model atmospheric state. For LOS wind analysis, the B covariance structures are crucial in both spatially interpolating the observed wind component and inferring the spatial pattern of the unobserved component of wind as well as the associated temperature and pressure increments. The design of the B matrix and the sampling strategy of the DWL space mission are the two most important factors that determine the impact of the data, both in real application and within the simplified framework of Riishojgaard et al. In the case in which B is poor, this would generally result in spatially poor analyses, especially when the
Riishojgaard等人(2004)的论文研究了前瞻性多普勒风激光雷达(DWL)视距(LOS)单视角风在气象分析中的同化和影响。认为单分量风观测在减少风分析误差方面远不如矢量风信息有效。这项工作具有重要的意义，因为未来天基DWL仪器将提供精确的单视角LOS风廓线测量。Riishojgaard等人正确地认为，这种风的用处需要在太空任务的设计阶段得到很好的解决。即将到来的欧洲空间局大气动力学任务(ADM)，称为Aeolus，就是在这种情况下提到的。Riishojgaard等人的研究是在一个理想化的、非常简化的框架下进行的。我们关注的是:1)简单的框架不能很好地代表用于数值天气预报(NWP)的最先进的全球数据同化系统的特征;2)所讨论的DWL情景具有丰富而不切实际的覆盖范围和质量。因此，他们的结论可能会误导人们，并且对可负担得起的基于空间的DWL的关键设计考虑贡献甚微。结果(以及分析风场的质量)可能更加真实，在我们看来，在一个更精心设计的实验中，对LOS风更有利。如果仅基于观测结果，NWP分析问题将严重不确定。为了克服这个问题，数据同化通常将相对稀疏的观测提供的信息与密集网格上的短期预报结合起来(Daley 1991)。由于NWP模型状态的观测很差，因此将局部观测增量在更大的区域内仔细分布是至关重要的。这个过程是基于背景误差结构的统计知识来完成的。在四维变分数据同化(4DVAR)分析系统中，还利用了模型状态的时间演化信息。在任何局部观测周围，背景误差的多变量空间相关信息(如背景误差协方差矩阵B所示)用于提供模式大气状态的空间相干更新。对于LOS风分析，B协方差结构在空间上插值观测到的风分量和推断未观测到的风分量的空间格局以及相关的温度和压力增量至关重要。无论是在实际应用中还是在Riishojgaard等人的简化框架中，DWL空间任务的B矩阵设计和采样策略都是决定数据影响的两个最重要的因素。在B较差的情况下，这通常会导致空间上较差的分析，特别是当观察值稀疏或未观察到一个或多个分析变量时。另一方面，在相对密集的观测网络中，与许多观测相关联的多元空间结构将重叠，不完美B的影响将减弱(通过过采样)。我们的具体意见在两个方面。首先是Riishojgaard等人的论文使用了合成涡流。通讯作者地址:Dr. Ad Stoffelen，荷兰皇家气象研究所，Postbus 201, 3730 AE de Bilt, Netherlands。电子邮件:ad.stoffelen@knmi.nl 1276 J O U R N A L O F P P L E D M E T E O R O L O G Y卷44
{"title":"Comments on \"The Impact of Doppler Lidar Wind Observations on a Single-Level Meteorological Analysis\"","authors":"A. Stoffelen, G. Marseille, E. Andersson, D. Tan","doi":"10.1175/JAM2268.1","DOIUrl":"https://doi.org/10.1175/JAM2268.1","url":null,"abstract":"The paper by Riishojgaard et al. (2004) investigates the assimilation and impact of prospective Doppler wind lidar (DWL) line-of-sight (LOS) single-perspective winds in meteorological analysis. It is argued that single-component wind observations are far less effective in reducing wind analysis error than vector wind information. This work has relevance because the prospects are good that space-based DWL instruments will provide accurate wind profiles of single-perspective LOS wind profile measurements in the future. Riishojgaard et al. rightly argue that the usefulness of such winds needs to be well addressed in the design phase of space missions. The forthcoming European Space Agency Atmospheric Dynamics Mission (ADM), called Aeolus, is referred to in this context. The Riishojgaard et al. study is carried out in an idealized and very simplified framework. Our concerns are 1) that the simple framework poorly represents the characteristics of a state-of-the-art global data assimilation system for numerical weather prediction (NWP) and 2) that the DWL scenarios that are discussed have abundant and unrealistic coverage and quality. As such, their conclusions may be misleading for, and contribute little toward, the critical design considerations for an affordable space-based DWL. The results (and the quality of the analyzed wind fields) could be far more realistic and, in our view, far more favorable for LOS winds in a more carefully designed experiment. The NWP analysis problem would be severely underdetermined if it were based on the observations alone. To overcome this problem, data assimilation typically combines the information provided by the relatively sparse observations with a short-range forecast on a dense grid (Daley 1991). Because the NWP model state is poorly observed, it is critical that local observation increments are carefully distributed spatially in a wider area. This process is done based on statistical knowledge of the background error structures. In a fourdimensional variational data assimilation (4DVAR) analysis system, information on the temporal evolution of the model state is also exploited. Around any local observation, information on the multivariate spatial correlation of the background errors, as represented in the background-error covariance matrix B, is used to provide a spatially coherent update of the model atmospheric state. For LOS wind analysis, the B covariance structures are crucial in both spatially interpolating the observed wind component and inferring the spatial pattern of the unobserved component of wind as well as the associated temperature and pressure increments. The design of the B matrix and the sampling strategy of the DWL space mission are the two most important factors that determine the impact of the data, both in real application and within the simplified framework of Riishojgaard et al. In the case in which B is poor, this would generally result in spatially poor analyses, especially when the ","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"114 1","pages":"1276-1277"},"PeriodicalIF":0.0,"publicationDate":"2005-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81054148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A better understanding of forest subcanopy flows is needed to evaluate their role in the horizontal movement of scalars, particularly in complex terrain. This paper describes detailed measurements of the canopy structure and its variability in both the horizontal and vertical directions at a deciduous forest in complex terrain (the Harvard Forest, Petersham, Massachusetts). The effects of the trunks and subcanopy shrubs on the flow field at each of six subcanopy array locations are quantified. The dynamics of the subcanopy flow are examined with pragmatic methods that can be implemented on a small scale with limited resources to estimate the stress divergence, buoyancy, and pressure gradient forces that drive the flow. The subcanopy flow at the Harvard Forest was driven by mechanisms other than vertical stress divergence 75% of the time. Nocturnal flows were driven predominantly by the negative buoyancy of a relatively cool layer near the forest floor. The direction of the resulting drainage flows followed the azimuth of the longest forest-floor slope. Similar results were found at a much flatter site at Borden, Ontario, Canada. There was no clear evidence of flow reversals in the subcanopy in the lee of ridges or hills at the Harvard Forest even in high wind conditions, contrary to some model predictions.
{"title":"Measuring Canopy Structure and the Kinematics of Subcanopy Flows in Two Forests","authors":"R. Staebler, D. Fitzjarrald","doi":"10.1175/JAM2265.1","DOIUrl":"https://doi.org/10.1175/JAM2265.1","url":null,"abstract":"A better understanding of forest subcanopy flows is needed to evaluate their role in the horizontal movement of scalars, particularly in complex terrain. This paper describes detailed measurements of the canopy structure and its variability in both the horizontal and vertical directions at a deciduous forest in complex terrain (the Harvard Forest, Petersham, Massachusetts). The effects of the trunks and subcanopy shrubs on the flow field at each of six subcanopy array locations are quantified. The dynamics of the subcanopy flow are examined with pragmatic methods that can be implemented on a small scale with limited resources to estimate the stress divergence, buoyancy, and pressure gradient forces that drive the flow. The subcanopy flow at the Harvard Forest was driven by mechanisms other than vertical stress divergence 75% of the time. Nocturnal flows were driven predominantly by the negative buoyancy of a relatively cool layer near the forest floor. The direction of the resulting drainage flows followed the azimuth of the longest forest-floor slope. Similar results were found at a much flatter site at Borden, Ontario, Canada. There was no clear evidence of flow reversals in the subcanopy in the lee of ridges or hills at the Harvard Forest even in high wind conditions, contrary to some model predictions.","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"38 1","pages":"1161-1179"},"PeriodicalIF":0.0,"publicationDate":"2005-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88628066","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Marshall, U. Lohmann, W. Leaitch, N. Shantz, L. Phinney, D. Toom‐Sauntry, Sangeeta Sharma
Abstract In July 2002, atmospheric aerosol measurements were conducted over the northeast Pacific Ocean as part of the Subarctic Ecosystem Response to Iron Enhancement Study (SERIES). The following aerosol quantities were measured: particle number size distribution, particle scattering and backscattering coefficients at three wavelengths, particle absorption coefficient at one wavelength, and size-segregated particle chemical composition. Using Mie theory to calculate the aerosol particle scattering and absorption coefficients from the size distribution and chemical measurements, closure with the measured optical coefficients is not attained. Discrepancies between the calculated and measured scattering and backscattering coefficients are largely a result of the fact that the nephelometer measures scattering only between 7° and 170°. Over 90% of the total scattering and 50% of the backscattering in this study was not measured by the nephelometer because of the missing forward-scattering (0°–7°) and backsca...
{"title":"Optical Properties of Aerosol Particles over the Northeast Pacific.","authors":"J. Marshall, U. Lohmann, W. Leaitch, N. Shantz, L. Phinney, D. Toom‐Sauntry, Sangeeta Sharma","doi":"10.1175/JAM2267.1","DOIUrl":"https://doi.org/10.1175/JAM2267.1","url":null,"abstract":"Abstract In July 2002, atmospheric aerosol measurements were conducted over the northeast Pacific Ocean as part of the Subarctic Ecosystem Response to Iron Enhancement Study (SERIES). The following aerosol quantities were measured: particle number size distribution, particle scattering and backscattering coefficients at three wavelengths, particle absorption coefficient at one wavelength, and size-segregated particle chemical composition. Using Mie theory to calculate the aerosol particle scattering and absorption coefficients from the size distribution and chemical measurements, closure with the measured optical coefficients is not attained. Discrepancies between the calculated and measured scattering and backscattering coefficients are largely a result of the fact that the nephelometer measures scattering only between 7° and 170°. Over 90% of the total scattering and 50% of the backscattering in this study was not measured by the nephelometer because of the missing forward-scattering (0°–7°) and backsca...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"337 1","pages":"1206-1220"},"PeriodicalIF":0.0,"publicationDate":"2005-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79736673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A brief review of errors associated with aircraft measurements of temperature in cumulus clouds is presented. This analysis forms the basis for the introduction of a compilation of in-cloud temperature measurements that the authors deem reliable. The measurements are mostly from radiometric thermometers, along with some carefully selected measurements taken with immersion thermometers. The data were collected in cumuli and cumulonimbi in Russia, the United States, and the central Pacific. An estimate of the in-cloud temperature measurement uncertainty is on the order of 0.5°C. The results suggest that the average temperature excess in cumulus clouds, when averaged over the cloud lifetime, is about 0.2°–0.3°C; this value may be biased to an unknown extent, however, by latencies inherent in identification and aircraft sampling of candidate clouds. The maximum temperature excess in growing cumulus congestus is about 2.5°–4°C. In the weak-echo regions of large thunderstorms, the temperature excess is at least 6°–8°C. The average and maximum temperature excesses in cumulus congestus over land are about 0.5°–1°C greater than over the ocean. Measurements of the spatial and vertical distributions of in-cloud temperature excess are presented. Some measurements that pertain to the structure of in-cloud temperature are also discussed.
{"title":"A Survey of Temperature Measurements in Convective Clouds","authors":"A. Sinkevich, R. P. Lawson","doi":"10.1175/JAM2247.1","DOIUrl":"https://doi.org/10.1175/JAM2247.1","url":null,"abstract":"A brief review of errors associated with aircraft measurements of temperature in cumulus clouds is presented. This analysis forms the basis for the introduction of a compilation of in-cloud temperature measurements that the authors deem reliable. The measurements are mostly from radiometric thermometers, along with some carefully selected measurements taken with immersion thermometers. The data were collected in cumuli and cumulonimbi in Russia, the United States, and the central Pacific. An estimate of the in-cloud temperature measurement uncertainty is on the order of 0.5°C. The results suggest that the average temperature excess in cumulus clouds, when averaged over the cloud lifetime, is about 0.2°–0.3°C; this value may be biased to an unknown extent, however, by latencies inherent in identification and aircraft sampling of candidate clouds. The maximum temperature excess in growing cumulus congestus is about 2.5°–4°C. In the weak-echo regions of large thunderstorms, the temperature excess is at least 6°–8°C. The average and maximum temperature excesses in cumulus congestus over land are about 0.5°–1°C greater than over the ocean. Measurements of the spatial and vertical distributions of in-cloud temperature excess are presented. Some measurements that pertain to the structure of in-cloud temperature are also discussed.","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"49 1","pages":"1133-1145"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82240998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Guerova, E. Brockmann, F. Schubiger, J. Morland, C. Mätzler
Abstract In this paper an integrated assessment of the vertically integrated water vapor (IWV) measured by radiosonde, microwave radiometer (MWR), and GPS and modeled by the limited-area mesoscale model of MeteoSwiss is presented. The different IWV measurement techniques are evaluated through intercomparisons of GPS to radiosonde in Payerne, Switzerland, and to the MWR operated at the Institute of Applied Physics at the University of Bern in Switzerland. The validation of the IWV field of the nonhydrostatic mesoscale Alpine Model (aLMo) of MeteoSwiss is performed against 14 GPS sites from the Automated GPS Network of Switzerland (AGNES) in the period of 2001–03. The model forecast and the nudging analysis are evaluated, with special attention paid to the diurnal cycle. The results from the GPS–radiosonde intercomparison are in agreement, but with a bimodal distribution of the day-to-night basis. At 0000 UTC, the bias is negative (−0.4 kg m−2); at 1200 UTC, it is positive (0.9 kg m−2) and the variability i...
全文:html(摘要)本文综合评价了由探空仪、微波辐射计(MWR)和GPS测量并由MeteoSwiss有限区域中尺度模式模拟的垂直综合水汽(IWV)。通过将GPS与瑞士Payerne的无线电探空仪和瑞士伯尔尼大学应用物理研究所运行的MWR进行相互比较，评估了不同的IWV测量技术。利用2001 ~ 2003年瑞士气象台(MeteoSwiss)非流体静力中尺度高山模式(aLMo)在瑞士自动GPS网(AGNES)的14个GPS站点上进行了IWV场的验证。对模型预测和助推分析进行了评价，特别注意了日周期。gps -无线电探空仪相互比较的结果是一致的，但在日夜基础上呈双峰分布。在0000 UTC，偏差为负(- 0.4 kg m - 2);在1200 UTC，它是正的(0.9 kg m−2)，变异性i…
{"title":"An Integrated Assessment of Measured and Modeled Integrated Water Vapor in Switzerland for the Period 2001–03","authors":"G. Guerova, E. Brockmann, F. Schubiger, J. Morland, C. Mätzler","doi":"10.1175/JAM2255.1","DOIUrl":"https://doi.org/10.1175/JAM2255.1","url":null,"abstract":"Abstract In this paper an integrated assessment of the vertically integrated water vapor (IWV) measured by radiosonde, microwave radiometer (MWR), and GPS and modeled by the limited-area mesoscale model of MeteoSwiss is presented. The different IWV measurement techniques are evaluated through intercomparisons of GPS to radiosonde in Payerne, Switzerland, and to the MWR operated at the Institute of Applied Physics at the University of Bern in Switzerland. The validation of the IWV field of the nonhydrostatic mesoscale Alpine Model (aLMo) of MeteoSwiss is performed against 14 GPS sites from the Automated GPS Network of Switzerland (AGNES) in the period of 2001–03. The model forecast and the nudging analysis are evaluated, with special attention paid to the diurnal cycle. The results from the GPS–radiosonde intercomparison are in agreement, but with a bimodal distribution of the day-to-night basis. At 0000 UTC, the bias is negative (−0.4 kg m−2); at 1200 UTC, it is positive (0.9 kg m−2) and the variability i...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"22 1","pages":"1033-1044"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86338647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract An Atmospheric Radiation and Cloud Station (ARCS) was established on the island of Nauru by the Atmospheric Radiation Measurement (ARM) Program. Analysis of the Nauru99 field experiment data indicated that measurements at the ARCS were affected by a cloud plume that was induced by diurnal heating of the island. During the Nauru Island Effects Study, instrumentation was installed at a second site to develop criteria for identifying when the cloud plume occurs and to quantify its effect on ARCS measurements. The plume directional heading and frequency of occurrence are affected by the large-scale tropical circulation. During the present study, in which an El Nino was developing, Nauru was in a region of active convection, and easterly trade winds were not dominant; plumes were observed in 25% of satellite images, and only one-half of the observed plumes were downwind of the ARCS site. Surface wind direction, surface air temperature, and downwelling solar radiation at the two sites were used to iden...
{"title":"Impact of Island-Induced Clouds on Surface Measurements: Analysis of the ARM Nauru Island Effect Study Data","authors":"S. McFarlane, C. Long, Donna Flynn","doi":"10.1175/JAM2241.1","DOIUrl":"https://doi.org/10.1175/JAM2241.1","url":null,"abstract":"Abstract An Atmospheric Radiation and Cloud Station (ARCS) was established on the island of Nauru by the Atmospheric Radiation Measurement (ARM) Program. Analysis of the Nauru99 field experiment data indicated that measurements at the ARCS were affected by a cloud plume that was induced by diurnal heating of the island. During the Nauru Island Effects Study, instrumentation was installed at a second site to develop criteria for identifying when the cloud plume occurs and to quantify its effect on ARCS measurements. The plume directional heading and frequency of occurrence are affected by the large-scale tropical circulation. During the present study, in which an El Nino was developing, Nauru was in a region of active convection, and easterly trade winds were not dominant; plumes were observed in 25% of satellite images, and only one-half of the observed plumes were downwind of the ARCS site. Surface wind direction, surface air temperature, and downwelling solar radiation at the two sites were used to iden...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"6 1","pages":"1045-1065"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87295906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. S. Shen, H. Yin, K. Cannon, A. Howard, S. Chetner, T. Karl
Abstract This paper analyzes the long-term (1901–2002) temporal trends in the agroclimate of Alberta, Canada, and explores the spatial variations of the agroclimatic resources and the potential crop-growing area in Alberta. Nine agroclimatic parameters are investigated: May–August precipitation (PCPN), the start of growing season (SGS), the end of the growing season (EGS), the length of the growing season (LGS), the date of the last spring frost (LSF), the date of the first fall frost (FFF), the length of the frost-free period (FFP), growing degree-days (GDDs), and corn heat units (CHUs). The temporal trends in the agroclimatic parameters are analyzed by using linear regression. The significance tests of the trends are made by using Kendall’s tau method. The results support the following conclusions. 1) The Alberta PCPN has increased 14% from 1901 to 2002, and the increment is the largest in the north and the northwest of Alberta, then diminishes (or even becomes negative over two small areas) in central ...
{"title":"Temporal and Spatial Changes of the Agroclimate in Alberta, Canada, from 1901 to 2002","authors":"S. S. Shen, H. Yin, K. Cannon, A. Howard, S. Chetner, T. Karl","doi":"10.1175/JAM2251.1","DOIUrl":"https://doi.org/10.1175/JAM2251.1","url":null,"abstract":"Abstract This paper analyzes the long-term (1901–2002) temporal trends in the agroclimate of Alberta, Canada, and explores the spatial variations of the agroclimatic resources and the potential crop-growing area in Alberta. Nine agroclimatic parameters are investigated: May–August precipitation (PCPN), the start of growing season (SGS), the end of the growing season (EGS), the length of the growing season (LGS), the date of the last spring frost (LSF), the date of the first fall frost (FFF), the length of the frost-free period (FFP), growing degree-days (GDDs), and corn heat units (CHUs). The temporal trends in the agroclimatic parameters are analyzed by using linear regression. The significance tests of the trends are made by using Kendall’s tau method. The results support the following conclusions. 1) The Alberta PCPN has increased 14% from 1901 to 2002, and the increment is the largest in the north and the northwest of Alberta, then diminishes (or even becomes negative over two small areas) in central ...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"78 1","pages":"1090-1105"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91228598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In mid-autumn 2002, an exceptional 5-day cold spell affected much of the interior Pacific Northwest, with minimum temperatures averaging 13[degree]C below long-term means (1953-21)112). On 31 October, minimum temperature records occurred at 98 of the 106 recording stations, with records lowered in some locations by 9[degree]C. Calculation of recurrence intervals of minimum temperatures shows that 50[percent][percent] of the stations experienced a >500-yr event. The synoptic conditions responsible were the development of a pronounced high pressure ridge over western Canada and an intense low pressure area centered in the Intermountain West that promoted strong northeasterly winds. The cold spell occurred near the end of the growing season for an ecologically critical and dominant tree species of the interior Pacific Northwest--western juniper--and followed an extended period of severe drought. In spring 2003, it became apparent that the cold had caused high rates of tree mortality and canopy dieback in a species that is remarkable for its longevity and resistance to climatic stress. The cold event altered western juniper dominance in some areas, and this alteration may have long-tern impacts on water budgets, fire intensities and frequencies, animal species interrelationships, and interspecific competition among plant species.
{"title":"Impacts of an extreme early-season freeze event in the Interior Pacific Northwest (30 October-3 November 2002) on Western juniper woodlands","authors":"P. Knapp, P. T. Soulé","doi":"10.1175/JAM2261.1","DOIUrl":"https://doi.org/10.1175/JAM2261.1","url":null,"abstract":"In mid-autumn 2002, an exceptional 5-day cold spell affected much of the interior Pacific Northwest, with minimum temperatures averaging 13[degree]C below long-term means (1953-21)112). On 31 October, minimum temperature records occurred at 98 of the 106 recording stations, with records lowered in some locations by 9[degree]C. Calculation of recurrence intervals of minimum temperatures shows that 50[percent][percent] of the stations experienced a >500-yr event. The synoptic conditions responsible were the development of a pronounced high pressure ridge over western Canada and an intense low pressure area centered in the Intermountain West that promoted strong northeasterly winds. The cold spell occurred near the end of the growing season for an ecologically critical and dominant tree species of the interior Pacific Northwest--western juniper--and followed an extended period of severe drought. In spring 2003, it became apparent that the cold had caused high rates of tree mortality and canopy dieback in a species that is remarkable for its longevity and resistance to climatic stress. The cold event altered western juniper dominance in some areas, and this alteration may have long-tern impacts on water budgets, fire intensities and frequencies, animal species interrelationships, and interspecific competition among plant species.","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"50 1","pages":"1152-1158"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74656122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The retrieval errors of cloud and precipitation hydrometeor contents from spaceborne observations are estimated at microwave frequencies in atmospheric windows between 18 and 150 GHz and in oxygen absorption complexes near 50–60 and 118 GHz. The method is based on a variational retrieval framework using a priori information on the cloud, atmosphere, and surface states from ECMWF short-range forecasts under different weather regimes. This approach was chosen because a consistent description of the model state and its uncertainties is provided, which is unavailable for other methods. The results show that the sounding channels provide more stable, more accurate, and less biased retrievals than window channels—in particular, over land surfaces and with regard to snowfall. Average performance estimates showed that if sounding channels are used, 80% of all retrievals are within 100% error limits and 60% of them are within 50% error limits with regard to rainfall. For snowfall, the sounding channels pr...
{"title":"Hydrometeor Retrieval Accuracy Using Microwave Window and Sounding Channel Observations","authors":"P. Bauer, E. Moreau, S. Michele","doi":"10.1175/JAM2257.1","DOIUrl":"https://doi.org/10.1175/JAM2257.1","url":null,"abstract":"Abstract The retrieval errors of cloud and precipitation hydrometeor contents from spaceborne observations are estimated at microwave frequencies in atmospheric windows between 18 and 150 GHz and in oxygen absorption complexes near 50–60 and 118 GHz. The method is based on a variational retrieval framework using a priori information on the cloud, atmosphere, and surface states from ECMWF short-range forecasts under different weather regimes. This approach was chosen because a consistent description of the model state and its uncertainties is provided, which is unavailable for other methods. The results show that the sounding channels provide more stable, more accurate, and less biased retrievals than window channels—in particular, over land surfaces and with regard to snowfall. Average performance estimates showed that if sounding channels are used, 80% of all retrievals are within 100% error limits and 60% of them are within 50% error limits with regard to rainfall. For snowfall, the sounding channels pr...","PeriodicalId":15026,"journal":{"name":"Journal of Applied Meteorology","volume":"108 1","pages":"1016-1032"},"PeriodicalIF":0.0,"publicationDate":"2005-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76036043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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